he stayed at FHQ Wehrwolf only three times:
16 July to 30 October 1942. The weather was hot, up to +45C, and the bunkers were humid. Hitler caught severe influenza, with a temperature running up to 40C. In this condition he gave his fateful decree no 45 and split his army group "South" into two parts, trying to reach both Stalingrad and the Caucasus oil fields simultaneously.
19 February to 13 March 1943.
27 August to 15 September 1943.

"Anyone know if Hitler visit east front during summer 1942 and if yes, where?"

The Wikipedia has a good article about Hitler's various command bunkers under Wehrwolf; a typical Nazi play on words. They have a map and also a shot of the concrete remains. The bunker/complex you are asking about is the one furthest right deep in the Ukraine. Jonny :smoke: